The capability of running programs made up of instructions.
The interaction with the user through the keyboard and the display.
The access to the file system.
Architecture and planning
The development of the system will be carried out in three phases, each
providing a working prototype.
Prototype 1: Hard-wired program . This is a simplified version of the Von
Neumann architecture: the CPU executes a predefined set of instructions
that are hard-wired in the code and not loaded from the RAM.
Prototype 2: Volatile programs . The CPU fetches the instructions loaded
from the RAM.
Prototype 3: Persistent programs . The CPU loads the program from the
Prototype 1: Hard-wired program
This prototype reflects a simplified Von Neumann architecture. The difference
with respect to a full architecture is that the CPU does not fetch the instructions
from the memory; instead it executes a fixed hard-wired program.
The computer architecture we want to implement is depicted in Figure 5.2.
The largest grained concept we want to represent is the computer (see
A computer is made up of a CPU, a bus and a RAM. This is represented by
the composition relationship. The semantics of such a relationship are that
a computer exists as long as its components exist, and the components
cannot stand by themselves. While this strong assumption may seem too
Figure 5.4 Analysis diagram of the simplified Von Neumann architecture